Technical Field
The present invention relates to a method for measuring underground boring position and an underground boring position measuring apparatus, and particularly relates to such a method and apparatus used in non-open cut working method performed without open cut of the ground.
Description of Related Art
A non-open cut method is a boring method of an energy saving type for burying water piping, gas piping or the like without performing open cut of the ground and it is expected to be utilized in the case of ground improvement working directly under the structures having been already constructed as a measure against ground liquefaction brought by earthquake or in the case of underground boring generally in a large scale without performing open cut.
On the other hand, in order to perform boring along a preset course without performing open cut of the ground in non-open cut working method, it is necessary to grasp the top position of the boring at all time on the ground. For measuring the position of the bit at the top of the boring used in a non-open cut working method, a measuring method is conventionally used such as to presume the position of the bit by receiving, on the ground, the electromagnetic signal issuing from the sensor attached to the top of the boring tool positioned underground. However, with this measuring method, the position of the bit cannot be measured in a situation where there are some obstacles upward from the position for measurement such as a construction, a river, etc.
Patent Document 1 discloses an example of conventional underground position measuring apparatus. In this apparatus, an accelerometer and a gyroscope are provided in a moving tool for moving in an intricate space in water or underground and the position is obtained through calculation using an angular velocity measured with a gyroscope and an acceleration measured with an accelerometer. Patent Document 2 discloses a method and an apparatus for measuring direction and inclination, in which a measured body having a conical measured face is held, within the apparatus body, in a freely inclining manner at the point in the direction through the apex of the cone, a displacement measurer with a light emitting portion irradiating laser beam to the conical measured face and a light receiving portion is provided and the inclination direction of the measured face is obtained by analyzing the displacement of the relative distance. Further, Patent Document 3 discloses detection of boring position, in which a rolling angle of the gyroscope attached to the tube secondary from the outside in a multilayered tube is detected and rolling angle is cancelled by detaching a clutch when the rolling angle has exceeded a predetermined value.